This invention relates to a machine for locating an operator with respect to an object and more particularly to a versatile machine tool in which the tool can be moved in three lineal directions and three rotational directions in relation to the surface of a workpiece.
Until recently, the most versatile form of cutting tool type machine tool was the so-called machining center which typically included a bed supporting a rotary table, an upright column and a spindle head carried by the column. Such a machining center can accomplish milling, drilling, boring and tapping operations in up to six axes of motion. Doing this requires that the movements of its table, column, spindle head, spindle and bed be coordinated and that the sometimes massive components be moved in very controllable finite increments. Although this type of modern machining center can provide very accurate machining, it becomes very complex and expensive when it is designed to provide maximum versatility.
In response to these problems, there was developed a different apparatus for locating a tool or another type of operator relative to a workpiece or other object. The apparatus employs a pair of spaced platforms, one of which may mount an operator such as a tool and the other may mount an object such as a workpiece. The spaced platforms are joined by six extensible legs, whose length may be individually manipulated to vary the position of the platforms and, therefore, the object and operator relative to each other in six axes. The legs may be powered. For example, they may be hydraulically driven cylinders or may be driven by a recirculating-ball screw. Applicants hereby incorporate by reference U.S. Pat. Nos. 4,988,244, Sheldon et al., Jan. 29, 1991 and 5,028,180, Sheldon, et al., Jul. 2, 1991, and PCT International Application Number PCT/US90/04797 published Mar. 21, 1991 under International Publication Number WO91/03145 ("the incorporated patent documents"). The incorporated patent documents disclose the inventions referred to in this paragraph.
One possible limitation to the versatility of the six-legged positioner is that it tends to impede easy movement of a workpiece onto the workpiece-holding platform and to restrict the size of the workpiece.